Investigations of the presence of caffeine in the Rudawa River, Kraków, Poland.

Caffeine concentration in surface water (Rudawa River, Kraków, Poland) has been being investigated since 2011. The method applied for investigations was developed in 2011, and the first series of measurements of caffeine concentration in surface water began in 2011. Caffeine concentration was determined by the gas chromatography-mass spectrometry (GC-MS) method. Solid phase extraction (SPE) was used to enrich the concentration of caffeine in water samples. As an internal standard, the caffeine isotope (13)C3 in methanol (Sigma Aldrich) was used. The values of four additional parameters (concentration of nitrates, biochemical oxygen demand after 7 days, number of Escherichia coli and number of Enterococcus faecalis) were determined for the water sample analyzed. Caffeine was detected in all studied samples. The control series of measurements during 2011-2014 confirmed that caffeine is present in Rudawa River water and that the concentration of this substance in Rudawa River ranges from 14.0 to 852.0 ng/dm(3). There is no correlation between the concentration of caffeine and the concentration of other anthropogenic contaminants determined in water.